CA1151299A - Method and apparatus for identifying objects - Google Patents
Method and apparatus for identifying objectsInfo
- Publication number
- CA1151299A CA1151299A CA000349940A CA349940A CA1151299A CA 1151299 A CA1151299 A CA 1151299A CA 000349940 A CA000349940 A CA 000349940A CA 349940 A CA349940 A CA 349940A CA 1151299 A CA1151299 A CA 1151299A
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- Prior art keywords
- signal
- line
- video signal
- contrasting
- line pattern
- Prior art date
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Classifications
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
- G06K7/00—Methods or arrangements for sensing record carriers, e.g. for reading patterns
- G06K7/10—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation
- G06K7/10544—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation by scanning of the records by radiation in the optical part of the electromagnetic spectrum
- G06K7/10821—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation by scanning of the records by radiation in the optical part of the electromagnetic spectrum further details of bar or optical code scanning devices
- G06K7/10861—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation by scanning of the records by radiation in the optical part of the electromagnetic spectrum further details of bar or optical code scanning devices sensing of data fields affixed to objects or articles, e.g. coded labels
- G06K7/10871—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation by scanning of the records by radiation in the optical part of the electromagnetic spectrum further details of bar or optical code scanning devices sensing of data fields affixed to objects or articles, e.g. coded labels randomly oriented data-fields, code-marks therefore, e.g. concentric circles-code
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
- G06K7/00—Methods or arrangements for sensing record carriers, e.g. for reading patterns
- G06K7/10—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation
- G06K7/14—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation using light without selection of wavelength, e.g. sensing reflected white light
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06V—IMAGE OR VIDEO RECOGNITION OR UNDERSTANDING
- G06V30/00—Character recognition; Recognising digital ink; Document-oriented image-based pattern recognition
- G06V30/10—Character recognition
- G06V30/22—Character recognition characterised by the type of writing
- G06V30/224—Character recognition characterised by the type of writing of printed characters having additional code marks or containing code marks
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- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Computer Vision & Pattern Recognition (AREA)
- Electromagnetism (AREA)
- Theoretical Computer Science (AREA)
- General Physics & Mathematics (AREA)
- General Health & Medical Sciences (AREA)
- Artificial Intelligence (AREA)
- Toxicology (AREA)
- Health & Medical Sciences (AREA)
- Multimedia (AREA)
- Character Input (AREA)
- Image Analysis (AREA)
- Control Of Vending Devices And Auxiliary Devices For Vending Devices (AREA)
- Vending Machines For Individual Products (AREA)
- Image Processing (AREA)
- Controls And Circuits For Display Device (AREA)
- Television Systems (AREA)
- Radar Systems Or Details Thereof (AREA)
- Signal Processing Not Specific To The Method Of Recording And Reproducing (AREA)
- Television Signal Processing For Recording (AREA)
- Exposure Control For Cameras (AREA)
- Signal Processing For Digital Recording And Reproducing (AREA)
- Cash Registers Or Receiving Machines (AREA)
- Automatic Analysis And Handling Materials Therefor (AREA)
Abstract
METHOD AND APPARATUS FOR IDENTIFYING OBJECTS
ABSTRACT
Disclosed is a method and an apparatus for identi-fying objects, such as articles sold in a store, appearing in a random position and orientation and at random times on an image window. On a surface facing the image window, each object has an identification in the form of a field which comprises on at least one data track contrasting indicia with at least one contrasting line pattern identifying the posi-tion and the orientation of the data track. The track also includes a plurality of parallel lines with variable spacing and/or line widths. The image window is scanned line-by-line to generate a binary video signal which corresponds to the scanned contrast sequence. The length of the overlapping light and dark intervals of the video signal resulting from the scanning of the line pattern is measured and successively measured interval lengths are compared with each other and a comparison signal having a first amplitude is generated when the two interval lengths which are being compared have a predetermined ratio to each other which conforms to the spacing of corresponding pattern lines. An identification signal is emitted when during each of a number of successive comparison steps, the number of which is determined by the contrasting line pattern, a reference signal having the first amplitude is generated.
ABSTRACT
Disclosed is a method and an apparatus for identi-fying objects, such as articles sold in a store, appearing in a random position and orientation and at random times on an image window. On a surface facing the image window, each object has an identification in the form of a field which comprises on at least one data track contrasting indicia with at least one contrasting line pattern identifying the posi-tion and the orientation of the data track. The track also includes a plurality of parallel lines with variable spacing and/or line widths. The image window is scanned line-by-line to generate a binary video signal which corresponds to the scanned contrast sequence. The length of the overlapping light and dark intervals of the video signal resulting from the scanning of the line pattern is measured and successively measured interval lengths are compared with each other and a comparison signal having a first amplitude is generated when the two interval lengths which are being compared have a predetermined ratio to each other which conforms to the spacing of corresponding pattern lines. An identification signal is emitted when during each of a number of successive comparison steps, the number of which is determined by the contrasting line pattern, a reference signal having the first amplitude is generated.
Description
~151299 METHOD AND APPARATUS FOR IDENTIFYING OBJECTS
The invention relates to a method and an apparatus for identifyin~ objects appearing in a random position and orientation and at random times on an image window. On a surface facing the image window, each object has an identi-fication in the form of a field which comprises on at least one data track contrasting indicia with at least one con-trasting line pattern identifying the position and the orientation of the data track. The track also includes a plurality of parallel lines with variable spacing and/or line widths. The image window is scanned line-by-line and a binary video signal i8 generated which corresponds to the scanned contrast sequ~ence. In a first step, the image window is scanned from varying angles or directions until a con-trasting line pattern is detected. In a second step, the position and alignment of the data field relative to the image window is determined and in a third step, raster scan is preformed in the direction of the data track to read and decode the indicia present on the data track.
Such method and apparatus are already known. The objectæ to be identified are, for example, commercial ~oods, department store articles, or the like which are identified in machine readable form. For this purpose, appropriate identifications are applied to the objects by imprlnting thereon with the desired code, for example the OCR code. The uncoded information may comprise indications of quality size, price, the number of the articles, and so forth.
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~51299 It is difficult to machine read such codes since the objects vary in size and since the code is frequently printed on adhesive labels which are applied to varying points on the article. Therefore, it cannot be assumed that the information can be found in a specific location with a fixed orientation and at predetermined time intervals. Thus, the reading of such codes cannot be compared with the reading of punched cards or the like, where a card is available in a precisely defined reading position at precisely fixed times.
In the present case, the exact opposite applies. The data field on the object appears only more or less approximately at a speciic place, and the alignment of the data field is to some extent arbitrary.
This type of method and apparatus for the identifi-cation of an object is used, for example, at the cashcounters of supermarkets and the like in order to identify the price and/or the number of the articles which a customer wishes to buy and which he has brought to the cash counter for this purpose. The articles, such as boxes of varying shape and size, bottles, cartons, cans, and the like, are then placed individually into the image window with the surface bearing the data field directed toward the image window. The data fields on the various objects thus appear in variable alignment at differing locations within the image window. The data fields also do not appear at the scanning station at fixed time intervals. Thus, the scanning station must be able to search for the data field and, once found, must readout the data track signals in the direction of the - data tracks of the field. The readout signals can then be fed to the cash register in the form of electric impulses so that the cash register can print out on the cash receipt the price, the number of the article, its classification, etc.
The data field applied onto the object is provided with a contrasting line pattern or product identification code ("PIC") which is defined by a plurality of parallel lines of varying spacing and/or line width. The purpose of the contrasting line pattern is to reliably and clearly distinguish the data field, for example the printed label, llSlZ~9 from other indicia or line patterns which may be present on the object in the vicinity of the data field. Further, within the data field the contrasting line pattern has a given position and orientation which can be used to ascertain the position and orientation of the contrasting line pat-tern -- ~nd thereby of the data tracks -- relative to the scanning angle of the scanning line. This can then be used to subsequently ras~er scan the field in the direction of the data tracks perpendicularly over the code lines. Thus, the reliable identification of the contrasting line pattern represents an important step in the omnidirectional reading of visibly imprinted data fields.
The German Offenlegungsschrift 2,338,561 discloses a method and an apparatus of the above described type wherein the identification of the contrasting line pattern occurs only when the lines of the pattern are oriented substantially perpendicularly to the scanning direction and the resulting pulse sequence of a video signal generated thereby eguals a predetermined pulse sequence which corresponds to the con-trasting line pattern used. In other words, theOffenlegungsschrift discloses a correlation method. It is particularly disadvantageous that the scanning of the image field for locating the contrasting line pattern must proceed ` in very small angular increments until a scanning line trans-sects the pattern vertically. This results in an undesire-ably long search time. Further, blurred printed edges of the contrasting line pattern may prevent a recognition of the pattern since in such an event the scanned pulse seguence and the resulting video signal may deviate from the stored refer-ence pattern. As a result, either the search process must berepeated or the contrasting line pattern is not recognized at all, leaving the associated data field unread.
In contrast, it is an object of the invention to provide a method and an apparatus of the above described type which make possible a rapid and reliable identification of contrasting line patterns while generally preventing blurred edges of the lines from adversely affecting the readout.
llS1299 In accordance with the invention this is achieved by measuring the len~th of the overlapping light and dark intervals of the video signal resulting from a scanning of ; the line pattern. Successively measured interval lengths are S compared with each other and a reference or comparison signal having a first amplitude is generated when the two interval lengths which are being compared have a predetermined ratio to each other which conforms to the spacing of corresponding pattern lines. An identification signal (PIC OUT] is emitted when during each of a number of successive comparison steps, the number of which is determined by the contrasting line pattern, a reference signal having the first amplitude is ge~erated. The comparing of successively measured interval lengths is carried out in pairs in a two dimensional comparison table within which the possible discrete values of an interval length are assigned to table lines, and the possible discrete values of the next following measured interval length are assigned to table columns. An expected field is specified encompassing the positions on the table in which the quotient of the two successively measured compared interval lengths falls within a given value range. The comparison or reference signal having the first amplitude is generated when the compared interval lengths correspond to a table position within the expected field.
The apparatus of the invention has an optoelec-tronic scanner which outputs binary video signals that cor-respond to the line-by-line scanned image field and comprises a series of light and dark intervals. The apparatus has a decoder for identifying a scanned contrasting line pattern of a plurality of parallel lines with varying spacing and/or line widths which characterizes the position and orientation of at least one data track of the data field. The apparatus further includes means for aligning the scanner parallel to the data track and for reading the indicia of the scanned data track.
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-- ` 1151299 4a In accordance with the invention the apparatus is characterized by a counting circuit which receives the video signals and determines the length of successive, overlapping video signal intervals. Further, the apparatus has at least one reference table which receives successively counted interval lengths in pairs via a gate circuit and emits a comparison signal having a first amplitude when two compared intervals lengths have a given ratio which corresponds to the ratio of the corresponding interval of the contrasting line pattèrn. An evaluation circuit is provided which generates an identification signal (PI~ OUT) when a predetermined number o reference signals with a first amplitude have been generated.
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'" 115~29g s The advantages of the invention reside particularly in that the identification of the contrasting line pattern is dependent only on whe~her the ratio of successive overlapping interval lengths of the video signal lies within narrow ranges. As a result, the contrasting line pattern is reli-abily identified even when scanning at an oblique angle to lines of the pattern since the ratios of successively mea-sured interval lengths of th video signal are constant and do not vary with the scanning angle. Thus, a single scanning of the contrasting line pattern -- at any desired angle -- so long as all lines of the pattern are crossed, is sufficient for a reliable identification of the line pattern. The line pattern can, therefore, be rapidly identified with relatively few scans in which the angular inclination is varied in large increments.
The decoding of the video signal for detecting the contrasting line pattern in relation to the video signal must take place in real-time, that is substantially simultaneously with the generation of th video signal to ensure that the line pattern is identified anywhere within the video signal.
Therefore, the determination of whether the ratio of succes-sively measured interval lengths falls within a given value range, is carried out not by a division but by entering the value of the ratio into a two-dimensional comparison table, sometimes also called a division table. The table emits a reference signal of a given, first amplitude only when two interval lengths which are being compared lie in a predeter-mined field of the table where the quotient of the compared interval lengths has a value range which corresponds to that of the corresponding interval length of the searched for line pattern. The time and hardware consuming division process is thereby eliminated and real-time operation with regard to the video signal is maintained.
The comparison table is preferably in the form of a two-dimensional programmed read-only memory (PROM). The various possible discrete values of the first measured inter-val length address the lines of the memory. The various discrete values of the next following measured interval length address the columns of the memory. The expected field is defined so that it encompasses all storage points where the guotient of the interval length associated with the line address fall within a given value range. If a storage point within the expected field i6 addressed, then the PROM emits a comparis~n signal of a first amplitude which signals a partial identification of the line pattern. If, however, the storage point determined by the line column addresses lies outside the expected field then a comparison signal with a second amplitude is emitted to indicate that the quotient of the compared successive interval lengths lies outside the predetermined value range. When a reference signal with a second amplitude appears, the decoder is reset and ready for a new identification and decoding step.
Preferably, two interval lengths which are to be compared are fed into a separate comparison table with its own expected field and examined there with regard to their quotient value. Each individual comparison table preferably comprises as a separate PROM. This simplifies the control logic of the decoder.
In accordance with a preferred embodiment of the invention, eight bit memory positions are provided for the first PROM to compare the first and the second interval lengths as well as for the second PROM to compare the second - 25 and third interval lengths, and so forth. Thus, eight com-parison taoles, each with its own expected field can be accommodated in the PROM's, the first table being formed for example from the first bit of the memory positions, the second table from the second bit of the memory positions, and so forth. By selectively addressing and selectively reading out the table which is being used, it is possible to identify up to eight different contrasting line patterns with one ~ecoding circuit, thereby enhancing the utilization of the apparatus in accordance with one aspect of the invention.
; 35 When the scanning beam sweeps over a darkly colored area of the data field, the binary video signal has a first amplitude "Hi", and it has a second amplitude "Lo" when the scanning beam sweeps over a light, signal-free area of the 115~Z99 data field. The allocation of the amplitudes Hi and Lo is arbitrary, and a different allocation of the two amplitudes to light and dark areas of the data field is possible.
The intervals of the video signal, the length of which is to be measured, preerably extend from one ri~ing slope of the video signal to the next rising slope, as well as overlapping therewith from one falling slope of the video signal between the rising slopes to the next falling slope.
The third interval then extends from the second rising slope to a next rising slope, and so forth. The fact that the intervals extend from a rising slope to a rising slope, or from a falling slope to a falling slope ensures that blurred edges of the contrast lines of the contrasting line pat-tern -- which generally extend in the same direction and in the same manner on all contrast lin~s -- do not materially influence the interval lengths. Consequently the decoder can identify contrasting line patterns in accordance with the invention which were produced under variable printing conditions.
To enhance the reliability of the identification, contrasting line patterns having a signal-free lead zone of a given length can be employed. This lead zone is disposed ahead of the first line of the pattern. In such a case the measurement of the interval length is preferably initiated only when a signal-free lead zone of a predetermined length appears in the video dignal.
Measurement of the interval lengths is preferably terminated when a measured interval length exceeds a pre-determined maximum which equals the maximum interval length present in the contrasting line pattern. ~n ongoing measure-ment of the interval lengths is preferably also terminated when the ratio of two successively measured interval lengths falls outside the predetermined value range. In both cases, the object identifying process is brought to a halt at the earliest possible moment and the decoder is reset and ready for a new cycle.
The ongoing measurement of the interval lengths is preferably also terminated when a signal-free intermediate ~151Z99 zone of a predetermined duration which equals the maximum distance between the lines of the line pattern is detected.
The decoding device is then reset and is ready for a new cycle.
The contrasting line pattern further preferably has a signaL-free trailing zone the length of which corresponds, for example, to the length of the signal-free lead zone. In such an event a contrasting line pattern identification signal is preferably emitted only when the video signal also includes the signal-free trailing zone of predetermined length.
To enhance the redundancy of the identification process and thus reduce the probability of error, the same line is preferably scanned n times, and a contrasting line pattern identification signal is emitted only when the pat-tern has been successively identified n times.
The lengths of the overlapping intervals of the video signal are preferably digitally measured and for this purpose they are counted out in a counting circuit. The counting circuit includes a timing circuit which generates gate pulses of the same length as the corresponding intervals of the video signal. The length of a given interval of the video signal is measured with a counter which receives as an input the gate pulses of that interval. The inputs of the counters are further connected with a sync generator which emits sync pulses to the counters. The final count of the individual counters then corresponds to the length of the respective gate pulses and thereby to the length of the corresponding intervals. Successively counted interval values address the corresponding read-only memory after the subsequent interval value has been counted, and while coun-ting of further interval values may still continue.
Embodiments of the invention are hereinafter described in greater detail with reference to the following drawings:
Fig. 1 shows a first arrangement of a contrasting line pattern within a data field having a data track;
115~2~9 Fig. 2 shows a second arrangement of a contrasting line pattern within a data field;
Fig. 3 shows a third arrangement of a contra6ting line pattern within a data field;
Fig. 4 shows the light-dark distribution of various contrastlng line patterns taken perpendicular to the contrast lines;
Fig. 5 ~hows a portion of the video signal as a function of time which corresponds to the contrasting line pattern of ~ig. 4(a);
Fig. 6 is a block diagram of the counting circuit of the decoder;
Fig. 7 is a block diagram of the comparison table of the decoder;
Fig. 8 is another embodiment of the comparison table of the decoder;
Fig. 9 is a block diagram of the evaluation circuit of the decoder;
Fig. 10 is a schematic representation of the struc-ture of the comparison table;
Fig. 11 is a pulse diagram of the pulses generated in the timing circuit of the counting circuit; and Fig. 12 is a pulse diagram or the pulses processed within a selecting circuit.
Figs. 1 to 3 show a variety of object identifica-tions 50 such as adhesive price labels which are secured, for example, to a container, a package or on any other article (not separately shown), and which appear in random positions and orientations on an image window. The image window is defined, for example, by the optical aperture of a flying-- spot scanner such as a vidicon, which first scans the image window line-by-line, and then in a linewise ra6ter scan.
The identifications 50 have a data field which includes contrasting signals 52 in at least one date track 51 for identifying the object or article. The contra6ting 6ignals are preferably optical character signals of one of the known, machine readable types, for example OCR-A or OCR-B
characters.
' ' , 1151Z~9 A contrasting line pattern 54 -- often referred to as position identification code or "PIC" -- is in a predeter-mined position and orientation in relation to the date track and has a plurality of parallel contrast lines with varying spacing and/or line widths. In the embodiment shown in Fig.
1, the line pattern is located in advance of the date track, in the embodiment shown in Fig. 2 it is underneath the data track, and in the embodiment shown in Fig. 3 it is at the end of the data track. The contrasting line pattern 54 is asym-metrical in a direction perpendicular to the contrast linesso as to identify the data field with regard to the beginning and the end of the data tracks. The line patterns shown in Figs. 1 and 2 have a signal-free lead zone 56 and a signal-free trailing zone 58.
Although the illustrated line patterns have only three lines each, patterns having more than three lines may be used. Further -- and deviating from the illustration of Figs. 1 to 3 -- the patterns may be located at a different position and have a different orientation in relation to the data tracks. It is further possible to provide two or more line patterns on one identification field 50.
A shown in Fig. 1, the image window, or an image corresponding to the window, for example on the target of a vidicon, is scanned step-by-step under an angle a by at least one scan line 60. Before reading the data tracks, it is important to first reliably identify the line pattern and determine its position and orientation relative to the scan line ~0 of the scanning beam since the signals contained in the data track can then be read by subsequent raster scanning in the direction of the data track.
Fig. 4 shows the light-dark distribution of various three-line PIC patterns taken perpendicular to the direction of the individual lines which are all asymmetric and can therefore be used in accordance with the invention.
Fig. S shows a section of the video signal obtained from scanning a PIC pattern in accordance with Fig. 4(a) as an electric binary signal, the amplitude Hi being allocated to the dark areas of the pattern and the amplitude Lo to the --"` 11512~9 light areas of the pattern. Light-dark fluctuations within the individual lines and the spacings of the PIC pattern are eliminated from the electric signal immediately after scan-ning. The video sig~al section shown in Fig. 5 includes a signal free lead zone that corresponds to the lead zone 56 in Fig. 1, a first interval Tl which extends from the first ascending flank or slope to the second ascending flank or slope, a second interval T2 which extends from the first descending flank to the second descending flank, a third interval T3 which extends from the second ascending flank to the third ascending flank, and a fourth interval T4 which extends from the second descending flank to the third descending flank. It also includes a trailing zone that corresponds to the trailing zone 5~ of Fig. 1.
The PIC pattern, for example the one shown in Fig.
5, is decoded according to the delta distance method, which determines whether successive and overlapping intervals, that is Tl, T2 and T2, T3 and T3, T4 have a predetermined ratio relative to each other as given by the PIC pattern which is to be decoded. If the value of the quotients of successive overlapping interval lengths falls within predetermined value ranges, the size of the range being determined by printing blurrs or digitalization inaccuracies, then in all probabil-ity the searched-for PIC pattern is present.
Fig. 6 shows the counting circuit, which forms the input of the decoder of the invention, and which counts the interval lengths Tl to T4 and makes them available as binary values for further processing. The counting circuit contains a timing circuit 2 to which the video signal "VIDE0" is fed and which emits at a first output a first gate signal from a irst rising slope to a second rising slope of the video signal, a second gate signal T2 at a second output from a falling slope following the first rising slope to a second falling slope of the video signal, a third gate signal T3 at a third output from the second rising slope to the next, third, rising slope, and a fourth gate signal T4 at a fourth output from the second falling slope to the next, third, falling slope. See also the pulse schematic shown in Fig.
11 .
1~5~9~
The gate signals T1 and T4 are fed individually to the gate inputs G1 to G4 of the four counters 6, 8, 10 and 12, respectively. Each counter receives at its input CT1 to CT4 sync pulses from a sync generator 14 which are counted by the counters so long as the respective gate signals T1 to T4 are applied. The result obtained at the outpus TC1 to TC4 of the counters 6 to 12 then represents a measure for the length of the gate signals T1 to T4.
In the timing circuit 2, a release signal E2 is generated by the falling slope of the gate signal T2, a release signal E3 is generated by the falling slope of the gate signal T3, and a release signal E4 is generated by the falling slope of the gate signal T4. The release signals are emitted at separate outputs. The release signal E4 further generates a signal PWAIT the length of which corresponds to the signal-free trailing zone after the end of the gate signal T4, and it too is emitted at a separate output.
The counting circuit further includes a reset circuit 4 which receives the video signal VIDEO, and an external reset signal "RESET IN~' at a separate input at the start of each scan line. The reset circuit 4 emits a reset signal RESET to the reset inputs RS1 to RS4 of the counters 6 to 12 as well as to the timing circuit 2 and resets the counters 6 to 12 as well as the timing circuit 2 into an ~;~ 25 active starting condition when the video signal contains a signal-free section -- of an amplitude Lo -- which is larger -~ than the maximum scanning distance between the lines of the PIC patterns as given by the maximum spacing within the PIC
pattern, multiplied by the largest permissible scanning angle.
The counting circuit further contains an overflow sensor 40 which is responsive to an overflow or carryover output OVl to OV4 of the counters 6 to 12 and emits a reset signal "OV RESET", and then resets the decoder into a new state of readiness.
Fig. 7 shows an embodiment of the comparison table - of the decoder which includes a read-only memory or PROM 28.
PROM 28 is organized so that count TCl of the counter 6 ' 1~5~299 addresses individual lines of the memory matrix and count TC2 of the counter 8 addresses individual columns of the first memory matrix. Counts TC1 and TC2 are applied to PROM ~8 by the release signal E2 via the gate circuits 16, 18 after TC2 has been counted. The first memory matrix includes an expec-tancy field which encompasses the memory positions where the quotient ~f the line address and the column address falls within a predetermined value range. This value range cor-responds to the quotient of a first interval length to a second interval length of the PIC pattern under considera-tion. If a memory position within the expectancy field is addressed by counts TCl and TC2, a reference signal having a first amplitude, for example Hi, is emitted which signals that information had been scanned which corresponds to a portion of the PIC pattern under consideration.
To correspondingly compare the gate pulses T2 with gate pulse T3, the count TC2 of the second counter 8 addres-ses the lines of a second memory matrix, and the count TC3 of the third counter 10 addresses the columns of the second memory matrix. The addressing takes place via gates 20, 22 after the count TC3 has been counted and the counts TC2 and TC3 are sent to PROM 28 by the release signal E3. The second matrix also includes an expectancy field which encompasses the memory positions whose quotient of line address and column address falls within a predetermined range which is equal to the va]ue range of the quotient of the intervals of the PIC pattern corresponding to gate signals T2 and T3.
When a memory position in the expectancy field is addressed, a reference signal having a first amplitude, for example the amplitude Hi, is emitted. When a memory position outside the expected field is addressed, a reference signal having a second amplitude Lo is emitted.
Comparison of the count TC3 of the third counter 10 with the position TC4 is accomplished likewise by addressing lines and columns of a third memory matrix which also includes an expectancy field. When a memory position within the expectancy field is addressed, a reference signal having a first amplitude Hi is emitted. The third memory matrix is llSlZ99 addressed via gates 24, 26 after the count TC 4 of the fourth counter 12 has been counted and the counts TC3 and TC4 are sent to the PROM 28 by the release signal E4. Gates 16 to 26 comprise AND gates.
The release of comparison signals LPICl and l.PIC2 and LPIC3 is effected by the release signals EL2, EL3 and EL
4 which are obtained by delaying the release signals E2, E3, and E4 in the delay circuit 30; see also the pulse plan of Fig. 12. Read-out may only take place after the first, second and third memory matrix have been addressed.
As an alternative to the embodiment shown in Fig.
7, the first memory matrix may be defined by a first read-only memory, PROMl, the second memory matrix by a second read-only memory, PROM2, and the third memory matrix by a third read-only memory, PROM3. In this embodiment three read-only memories of relatively low storage capacity can be employed.
The read-only memory 28 has storage areas each of which has an n-bit capacity. Since for the determination of an expected field only one bit of the storage area portion defining the expected field is occupied, up to eight dif-ferent expected fields for eight different PIC patterns can be simultaneously accommodated in the PROM. For example, the first expected field in PROMl is accommodated in the first bit of the memory positions, the second expected field in the second bit of the memory positions, and so forth. The same applies for PROM2 and PROM3. The line and column addressing for a specific PIC pattern must then occur selectively to the corresponding bits of the memory positions. Further, a switch 32 coupled to PROM28 selectively reads out the com-parison signals LPICl and LPIC2 and LPIC3 from the pertinent bits of the memory positions and transmits as its output to an evaluation circuit the evaluation signal MUX PIC, formed of the sequential comparison signals LPICl, LPIC2 and LPIC3.
Fig. 9 illustrates the evaluation circuit of the decoding device. An interim memory 34 receives the evalua-tion signal MUX PIC and stores the comparison signal LPIC1 --which indicates that the value TC1/TC2 falls within a pre-l~S~;29~
determined range -- as well as comparison signals LPIC2 and LPIC3. Storing is commenced by release signals EL2 and EL3 and EL4 which are generated substantially simultaneously with the comparison signals LPIC1, LPIC2 and LPIC3, see the pulse schematic of Fig. 12. After all comparison signals have been stored Ln the interim memory as storage signals LPICl', LPIC2', LPIC3', the storage signals are transmitted to an AND
gate 36 which emits an output signal LPIC when all storage signals LPICl' etc. have a first amplitude corresponding to the first amplitude of the comparison signals LPICl etc., see Fig. 12. The output signal LPIC is fed to an output circuit 38 which receives the video signal VIDEO and the hold signal PWAIT from the control circuit 2. The output circuit 38 generates an identification signal "PIC OUT" when the video signal VIDEO remains on amplitude Lo while hold signal PWAIT
is applied. The amplitude Lo identifies a signal-free sub-surface. This ensures that the decoded line pattern is followed by a signal-free trailing zone which corresponds to the trailing zone 58 of the PIC pattern.
The output circuit 38 is reset by the external reset signal "RESET IN" and thereupon applies a reset signal RESETA to the interim memory 34 and resets the latter for a new cycle. The interim memory is further reset by the over-flow reset signal "OV RESET" when one of the counters 6 to 12 signals an overflow.
Fig. 10 is a schematic representation of the organ-ization of the comparison table, for example the partial comparison table of PROM1 for comparing the quotient TC1/TC2.
The table comprises a memory matrix and its lines and columns have the appropriate binary addresses. In accordance with a preferred em~odiment of the decoder of the invention, a 5-bit representation has been selected. All memory positions with a specific value of the quotient of line address to column address lie on one line, the so-called expectancy line around which the expectancy field is located. Within the field all those memory positions are located which address quotients that fall in the predetermined value range. The counts TCl to TC4 are also emitted as 5-bit words. The ount TCl ` llSlZ~9 addresses the lines of the table, the count TC2 addresses the col~mns of the table.
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The invention relates to a method and an apparatus for identifyin~ objects appearing in a random position and orientation and at random times on an image window. On a surface facing the image window, each object has an identi-fication in the form of a field which comprises on at least one data track contrasting indicia with at least one con-trasting line pattern identifying the position and the orientation of the data track. The track also includes a plurality of parallel lines with variable spacing and/or line widths. The image window is scanned line-by-line and a binary video signal i8 generated which corresponds to the scanned contrast sequ~ence. In a first step, the image window is scanned from varying angles or directions until a con-trasting line pattern is detected. In a second step, the position and alignment of the data field relative to the image window is determined and in a third step, raster scan is preformed in the direction of the data track to read and decode the indicia present on the data track.
Such method and apparatus are already known. The objectæ to be identified are, for example, commercial ~oods, department store articles, or the like which are identified in machine readable form. For this purpose, appropriate identifications are applied to the objects by imprlnting thereon with the desired code, for example the OCR code. The uncoded information may comprise indications of quality size, price, the number of the articles, and so forth.
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~51299 It is difficult to machine read such codes since the objects vary in size and since the code is frequently printed on adhesive labels which are applied to varying points on the article. Therefore, it cannot be assumed that the information can be found in a specific location with a fixed orientation and at predetermined time intervals. Thus, the reading of such codes cannot be compared with the reading of punched cards or the like, where a card is available in a precisely defined reading position at precisely fixed times.
In the present case, the exact opposite applies. The data field on the object appears only more or less approximately at a speciic place, and the alignment of the data field is to some extent arbitrary.
This type of method and apparatus for the identifi-cation of an object is used, for example, at the cashcounters of supermarkets and the like in order to identify the price and/or the number of the articles which a customer wishes to buy and which he has brought to the cash counter for this purpose. The articles, such as boxes of varying shape and size, bottles, cartons, cans, and the like, are then placed individually into the image window with the surface bearing the data field directed toward the image window. The data fields on the various objects thus appear in variable alignment at differing locations within the image window. The data fields also do not appear at the scanning station at fixed time intervals. Thus, the scanning station must be able to search for the data field and, once found, must readout the data track signals in the direction of the - data tracks of the field. The readout signals can then be fed to the cash register in the form of electric impulses so that the cash register can print out on the cash receipt the price, the number of the article, its classification, etc.
The data field applied onto the object is provided with a contrasting line pattern or product identification code ("PIC") which is defined by a plurality of parallel lines of varying spacing and/or line width. The purpose of the contrasting line pattern is to reliably and clearly distinguish the data field, for example the printed label, llSlZ~9 from other indicia or line patterns which may be present on the object in the vicinity of the data field. Further, within the data field the contrasting line pattern has a given position and orientation which can be used to ascertain the position and orientation of the contrasting line pat-tern -- ~nd thereby of the data tracks -- relative to the scanning angle of the scanning line. This can then be used to subsequently ras~er scan the field in the direction of the data tracks perpendicularly over the code lines. Thus, the reliable identification of the contrasting line pattern represents an important step in the omnidirectional reading of visibly imprinted data fields.
The German Offenlegungsschrift 2,338,561 discloses a method and an apparatus of the above described type wherein the identification of the contrasting line pattern occurs only when the lines of the pattern are oriented substantially perpendicularly to the scanning direction and the resulting pulse sequence of a video signal generated thereby eguals a predetermined pulse sequence which corresponds to the con-trasting line pattern used. In other words, theOffenlegungsschrift discloses a correlation method. It is particularly disadvantageous that the scanning of the image field for locating the contrasting line pattern must proceed ` in very small angular increments until a scanning line trans-sects the pattern vertically. This results in an undesire-ably long search time. Further, blurred printed edges of the contrasting line pattern may prevent a recognition of the pattern since in such an event the scanned pulse seguence and the resulting video signal may deviate from the stored refer-ence pattern. As a result, either the search process must berepeated or the contrasting line pattern is not recognized at all, leaving the associated data field unread.
In contrast, it is an object of the invention to provide a method and an apparatus of the above described type which make possible a rapid and reliable identification of contrasting line patterns while generally preventing blurred edges of the lines from adversely affecting the readout.
llS1299 In accordance with the invention this is achieved by measuring the len~th of the overlapping light and dark intervals of the video signal resulting from a scanning of ; the line pattern. Successively measured interval lengths are S compared with each other and a reference or comparison signal having a first amplitude is generated when the two interval lengths which are being compared have a predetermined ratio to each other which conforms to the spacing of corresponding pattern lines. An identification signal (PIC OUT] is emitted when during each of a number of successive comparison steps, the number of which is determined by the contrasting line pattern, a reference signal having the first amplitude is ge~erated. The comparing of successively measured interval lengths is carried out in pairs in a two dimensional comparison table within which the possible discrete values of an interval length are assigned to table lines, and the possible discrete values of the next following measured interval length are assigned to table columns. An expected field is specified encompassing the positions on the table in which the quotient of the two successively measured compared interval lengths falls within a given value range. The comparison or reference signal having the first amplitude is generated when the compared interval lengths correspond to a table position within the expected field.
The apparatus of the invention has an optoelec-tronic scanner which outputs binary video signals that cor-respond to the line-by-line scanned image field and comprises a series of light and dark intervals. The apparatus has a decoder for identifying a scanned contrasting line pattern of a plurality of parallel lines with varying spacing and/or line widths which characterizes the position and orientation of at least one data track of the data field. The apparatus further includes means for aligning the scanner parallel to the data track and for reading the indicia of the scanned data track.
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-- ` 1151299 4a In accordance with the invention the apparatus is characterized by a counting circuit which receives the video signals and determines the length of successive, overlapping video signal intervals. Further, the apparatus has at least one reference table which receives successively counted interval lengths in pairs via a gate circuit and emits a comparison signal having a first amplitude when two compared intervals lengths have a given ratio which corresponds to the ratio of the corresponding interval of the contrasting line pattèrn. An evaluation circuit is provided which generates an identification signal (PI~ OUT) when a predetermined number o reference signals with a first amplitude have been generated.
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'" 115~29g s The advantages of the invention reside particularly in that the identification of the contrasting line pattern is dependent only on whe~her the ratio of successive overlapping interval lengths of the video signal lies within narrow ranges. As a result, the contrasting line pattern is reli-abily identified even when scanning at an oblique angle to lines of the pattern since the ratios of successively mea-sured interval lengths of th video signal are constant and do not vary with the scanning angle. Thus, a single scanning of the contrasting line pattern -- at any desired angle -- so long as all lines of the pattern are crossed, is sufficient for a reliable identification of the line pattern. The line pattern can, therefore, be rapidly identified with relatively few scans in which the angular inclination is varied in large increments.
The decoding of the video signal for detecting the contrasting line pattern in relation to the video signal must take place in real-time, that is substantially simultaneously with the generation of th video signal to ensure that the line pattern is identified anywhere within the video signal.
Therefore, the determination of whether the ratio of succes-sively measured interval lengths falls within a given value range, is carried out not by a division but by entering the value of the ratio into a two-dimensional comparison table, sometimes also called a division table. The table emits a reference signal of a given, first amplitude only when two interval lengths which are being compared lie in a predeter-mined field of the table where the quotient of the compared interval lengths has a value range which corresponds to that of the corresponding interval length of the searched for line pattern. The time and hardware consuming division process is thereby eliminated and real-time operation with regard to the video signal is maintained.
The comparison table is preferably in the form of a two-dimensional programmed read-only memory (PROM). The various possible discrete values of the first measured inter-val length address the lines of the memory. The various discrete values of the next following measured interval length address the columns of the memory. The expected field is defined so that it encompasses all storage points where the guotient of the interval length associated with the line address fall within a given value range. If a storage point within the expected field i6 addressed, then the PROM emits a comparis~n signal of a first amplitude which signals a partial identification of the line pattern. If, however, the storage point determined by the line column addresses lies outside the expected field then a comparison signal with a second amplitude is emitted to indicate that the quotient of the compared successive interval lengths lies outside the predetermined value range. When a reference signal with a second amplitude appears, the decoder is reset and ready for a new identification and decoding step.
Preferably, two interval lengths which are to be compared are fed into a separate comparison table with its own expected field and examined there with regard to their quotient value. Each individual comparison table preferably comprises as a separate PROM. This simplifies the control logic of the decoder.
In accordance with a preferred embodiment of the invention, eight bit memory positions are provided for the first PROM to compare the first and the second interval lengths as well as for the second PROM to compare the second - 25 and third interval lengths, and so forth. Thus, eight com-parison taoles, each with its own expected field can be accommodated in the PROM's, the first table being formed for example from the first bit of the memory positions, the second table from the second bit of the memory positions, and so forth. By selectively addressing and selectively reading out the table which is being used, it is possible to identify up to eight different contrasting line patterns with one ~ecoding circuit, thereby enhancing the utilization of the apparatus in accordance with one aspect of the invention.
; 35 When the scanning beam sweeps over a darkly colored area of the data field, the binary video signal has a first amplitude "Hi", and it has a second amplitude "Lo" when the scanning beam sweeps over a light, signal-free area of the 115~Z99 data field. The allocation of the amplitudes Hi and Lo is arbitrary, and a different allocation of the two amplitudes to light and dark areas of the data field is possible.
The intervals of the video signal, the length of which is to be measured, preerably extend from one ri~ing slope of the video signal to the next rising slope, as well as overlapping therewith from one falling slope of the video signal between the rising slopes to the next falling slope.
The third interval then extends from the second rising slope to a next rising slope, and so forth. The fact that the intervals extend from a rising slope to a rising slope, or from a falling slope to a falling slope ensures that blurred edges of the contrast lines of the contrasting line pat-tern -- which generally extend in the same direction and in the same manner on all contrast lin~s -- do not materially influence the interval lengths. Consequently the decoder can identify contrasting line patterns in accordance with the invention which were produced under variable printing conditions.
To enhance the reliability of the identification, contrasting line patterns having a signal-free lead zone of a given length can be employed. This lead zone is disposed ahead of the first line of the pattern. In such a case the measurement of the interval length is preferably initiated only when a signal-free lead zone of a predetermined length appears in the video dignal.
Measurement of the interval lengths is preferably terminated when a measured interval length exceeds a pre-determined maximum which equals the maximum interval length present in the contrasting line pattern. ~n ongoing measure-ment of the interval lengths is preferably also terminated when the ratio of two successively measured interval lengths falls outside the predetermined value range. In both cases, the object identifying process is brought to a halt at the earliest possible moment and the decoder is reset and ready for a new cycle.
The ongoing measurement of the interval lengths is preferably also terminated when a signal-free intermediate ~151Z99 zone of a predetermined duration which equals the maximum distance between the lines of the line pattern is detected.
The decoding device is then reset and is ready for a new cycle.
The contrasting line pattern further preferably has a signaL-free trailing zone the length of which corresponds, for example, to the length of the signal-free lead zone. In such an event a contrasting line pattern identification signal is preferably emitted only when the video signal also includes the signal-free trailing zone of predetermined length.
To enhance the redundancy of the identification process and thus reduce the probability of error, the same line is preferably scanned n times, and a contrasting line pattern identification signal is emitted only when the pat-tern has been successively identified n times.
The lengths of the overlapping intervals of the video signal are preferably digitally measured and for this purpose they are counted out in a counting circuit. The counting circuit includes a timing circuit which generates gate pulses of the same length as the corresponding intervals of the video signal. The length of a given interval of the video signal is measured with a counter which receives as an input the gate pulses of that interval. The inputs of the counters are further connected with a sync generator which emits sync pulses to the counters. The final count of the individual counters then corresponds to the length of the respective gate pulses and thereby to the length of the corresponding intervals. Successively counted interval values address the corresponding read-only memory after the subsequent interval value has been counted, and while coun-ting of further interval values may still continue.
Embodiments of the invention are hereinafter described in greater detail with reference to the following drawings:
Fig. 1 shows a first arrangement of a contrasting line pattern within a data field having a data track;
115~2~9 Fig. 2 shows a second arrangement of a contrasting line pattern within a data field;
Fig. 3 shows a third arrangement of a contra6ting line pattern within a data field;
Fig. 4 shows the light-dark distribution of various contrastlng line patterns taken perpendicular to the contrast lines;
Fig. 5 ~hows a portion of the video signal as a function of time which corresponds to the contrasting line pattern of ~ig. 4(a);
Fig. 6 is a block diagram of the counting circuit of the decoder;
Fig. 7 is a block diagram of the comparison table of the decoder;
Fig. 8 is another embodiment of the comparison table of the decoder;
Fig. 9 is a block diagram of the evaluation circuit of the decoder;
Fig. 10 is a schematic representation of the struc-ture of the comparison table;
Fig. 11 is a pulse diagram of the pulses generated in the timing circuit of the counting circuit; and Fig. 12 is a pulse diagram or the pulses processed within a selecting circuit.
Figs. 1 to 3 show a variety of object identifica-tions 50 such as adhesive price labels which are secured, for example, to a container, a package or on any other article (not separately shown), and which appear in random positions and orientations on an image window. The image window is defined, for example, by the optical aperture of a flying-- spot scanner such as a vidicon, which first scans the image window line-by-line, and then in a linewise ra6ter scan.
The identifications 50 have a data field which includes contrasting signals 52 in at least one date track 51 for identifying the object or article. The contra6ting 6ignals are preferably optical character signals of one of the known, machine readable types, for example OCR-A or OCR-B
characters.
' ' , 1151Z~9 A contrasting line pattern 54 -- often referred to as position identification code or "PIC" -- is in a predeter-mined position and orientation in relation to the date track and has a plurality of parallel contrast lines with varying spacing and/or line widths. In the embodiment shown in Fig.
1, the line pattern is located in advance of the date track, in the embodiment shown in Fig. 2 it is underneath the data track, and in the embodiment shown in Fig. 3 it is at the end of the data track. The contrasting line pattern 54 is asym-metrical in a direction perpendicular to the contrast linesso as to identify the data field with regard to the beginning and the end of the data tracks. The line patterns shown in Figs. 1 and 2 have a signal-free lead zone 56 and a signal-free trailing zone 58.
Although the illustrated line patterns have only three lines each, patterns having more than three lines may be used. Further -- and deviating from the illustration of Figs. 1 to 3 -- the patterns may be located at a different position and have a different orientation in relation to the data tracks. It is further possible to provide two or more line patterns on one identification field 50.
A shown in Fig. 1, the image window, or an image corresponding to the window, for example on the target of a vidicon, is scanned step-by-step under an angle a by at least one scan line 60. Before reading the data tracks, it is important to first reliably identify the line pattern and determine its position and orientation relative to the scan line ~0 of the scanning beam since the signals contained in the data track can then be read by subsequent raster scanning in the direction of the data track.
Fig. 4 shows the light-dark distribution of various three-line PIC patterns taken perpendicular to the direction of the individual lines which are all asymmetric and can therefore be used in accordance with the invention.
Fig. S shows a section of the video signal obtained from scanning a PIC pattern in accordance with Fig. 4(a) as an electric binary signal, the amplitude Hi being allocated to the dark areas of the pattern and the amplitude Lo to the --"` 11512~9 light areas of the pattern. Light-dark fluctuations within the individual lines and the spacings of the PIC pattern are eliminated from the electric signal immediately after scan-ning. The video sig~al section shown in Fig. 5 includes a signal free lead zone that corresponds to the lead zone 56 in Fig. 1, a first interval Tl which extends from the first ascending flank or slope to the second ascending flank or slope, a second interval T2 which extends from the first descending flank to the second descending flank, a third interval T3 which extends from the second ascending flank to the third ascending flank, and a fourth interval T4 which extends from the second descending flank to the third descending flank. It also includes a trailing zone that corresponds to the trailing zone 5~ of Fig. 1.
The PIC pattern, for example the one shown in Fig.
5, is decoded according to the delta distance method, which determines whether successive and overlapping intervals, that is Tl, T2 and T2, T3 and T3, T4 have a predetermined ratio relative to each other as given by the PIC pattern which is to be decoded. If the value of the quotients of successive overlapping interval lengths falls within predetermined value ranges, the size of the range being determined by printing blurrs or digitalization inaccuracies, then in all probabil-ity the searched-for PIC pattern is present.
Fig. 6 shows the counting circuit, which forms the input of the decoder of the invention, and which counts the interval lengths Tl to T4 and makes them available as binary values for further processing. The counting circuit contains a timing circuit 2 to which the video signal "VIDE0" is fed and which emits at a first output a first gate signal from a irst rising slope to a second rising slope of the video signal, a second gate signal T2 at a second output from a falling slope following the first rising slope to a second falling slope of the video signal, a third gate signal T3 at a third output from the second rising slope to the next, third, rising slope, and a fourth gate signal T4 at a fourth output from the second falling slope to the next, third, falling slope. See also the pulse schematic shown in Fig.
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The gate signals T1 and T4 are fed individually to the gate inputs G1 to G4 of the four counters 6, 8, 10 and 12, respectively. Each counter receives at its input CT1 to CT4 sync pulses from a sync generator 14 which are counted by the counters so long as the respective gate signals T1 to T4 are applied. The result obtained at the outpus TC1 to TC4 of the counters 6 to 12 then represents a measure for the length of the gate signals T1 to T4.
In the timing circuit 2, a release signal E2 is generated by the falling slope of the gate signal T2, a release signal E3 is generated by the falling slope of the gate signal T3, and a release signal E4 is generated by the falling slope of the gate signal T4. The release signals are emitted at separate outputs. The release signal E4 further generates a signal PWAIT the length of which corresponds to the signal-free trailing zone after the end of the gate signal T4, and it too is emitted at a separate output.
The counting circuit further includes a reset circuit 4 which receives the video signal VIDEO, and an external reset signal "RESET IN~' at a separate input at the start of each scan line. The reset circuit 4 emits a reset signal RESET to the reset inputs RS1 to RS4 of the counters 6 to 12 as well as to the timing circuit 2 and resets the counters 6 to 12 as well as the timing circuit 2 into an ~;~ 25 active starting condition when the video signal contains a signal-free section -- of an amplitude Lo -- which is larger -~ than the maximum scanning distance between the lines of the PIC patterns as given by the maximum spacing within the PIC
pattern, multiplied by the largest permissible scanning angle.
The counting circuit further contains an overflow sensor 40 which is responsive to an overflow or carryover output OVl to OV4 of the counters 6 to 12 and emits a reset signal "OV RESET", and then resets the decoder into a new state of readiness.
Fig. 7 shows an embodiment of the comparison table - of the decoder which includes a read-only memory or PROM 28.
PROM 28 is organized so that count TCl of the counter 6 ' 1~5~299 addresses individual lines of the memory matrix and count TC2 of the counter 8 addresses individual columns of the first memory matrix. Counts TC1 and TC2 are applied to PROM ~8 by the release signal E2 via the gate circuits 16, 18 after TC2 has been counted. The first memory matrix includes an expec-tancy field which encompasses the memory positions where the quotient ~f the line address and the column address falls within a predetermined value range. This value range cor-responds to the quotient of a first interval length to a second interval length of the PIC pattern under considera-tion. If a memory position within the expectancy field is addressed by counts TCl and TC2, a reference signal having a first amplitude, for example Hi, is emitted which signals that information had been scanned which corresponds to a portion of the PIC pattern under consideration.
To correspondingly compare the gate pulses T2 with gate pulse T3, the count TC2 of the second counter 8 addres-ses the lines of a second memory matrix, and the count TC3 of the third counter 10 addresses the columns of the second memory matrix. The addressing takes place via gates 20, 22 after the count TC3 has been counted and the counts TC2 and TC3 are sent to PROM 28 by the release signal E3. The second matrix also includes an expectancy field which encompasses the memory positions whose quotient of line address and column address falls within a predetermined range which is equal to the va]ue range of the quotient of the intervals of the PIC pattern corresponding to gate signals T2 and T3.
When a memory position in the expectancy field is addressed, a reference signal having a first amplitude, for example the amplitude Hi, is emitted. When a memory position outside the expected field is addressed, a reference signal having a second amplitude Lo is emitted.
Comparison of the count TC3 of the third counter 10 with the position TC4 is accomplished likewise by addressing lines and columns of a third memory matrix which also includes an expectancy field. When a memory position within the expectancy field is addressed, a reference signal having a first amplitude Hi is emitted. The third memory matrix is llSlZ99 addressed via gates 24, 26 after the count TC 4 of the fourth counter 12 has been counted and the counts TC3 and TC4 are sent to the PROM 28 by the release signal E4. Gates 16 to 26 comprise AND gates.
The release of comparison signals LPICl and l.PIC2 and LPIC3 is effected by the release signals EL2, EL3 and EL
4 which are obtained by delaying the release signals E2, E3, and E4 in the delay circuit 30; see also the pulse plan of Fig. 12. Read-out may only take place after the first, second and third memory matrix have been addressed.
As an alternative to the embodiment shown in Fig.
7, the first memory matrix may be defined by a first read-only memory, PROMl, the second memory matrix by a second read-only memory, PROM2, and the third memory matrix by a third read-only memory, PROM3. In this embodiment three read-only memories of relatively low storage capacity can be employed.
The read-only memory 28 has storage areas each of which has an n-bit capacity. Since for the determination of an expected field only one bit of the storage area portion defining the expected field is occupied, up to eight dif-ferent expected fields for eight different PIC patterns can be simultaneously accommodated in the PROM. For example, the first expected field in PROMl is accommodated in the first bit of the memory positions, the second expected field in the second bit of the memory positions, and so forth. The same applies for PROM2 and PROM3. The line and column addressing for a specific PIC pattern must then occur selectively to the corresponding bits of the memory positions. Further, a switch 32 coupled to PROM28 selectively reads out the com-parison signals LPICl and LPIC2 and LPIC3 from the pertinent bits of the memory positions and transmits as its output to an evaluation circuit the evaluation signal MUX PIC, formed of the sequential comparison signals LPICl, LPIC2 and LPIC3.
Fig. 9 illustrates the evaluation circuit of the decoding device. An interim memory 34 receives the evalua-tion signal MUX PIC and stores the comparison signal LPIC1 --which indicates that the value TC1/TC2 falls within a pre-l~S~;29~
determined range -- as well as comparison signals LPIC2 and LPIC3. Storing is commenced by release signals EL2 and EL3 and EL4 which are generated substantially simultaneously with the comparison signals LPIC1, LPIC2 and LPIC3, see the pulse schematic of Fig. 12. After all comparison signals have been stored Ln the interim memory as storage signals LPICl', LPIC2', LPIC3', the storage signals are transmitted to an AND
gate 36 which emits an output signal LPIC when all storage signals LPICl' etc. have a first amplitude corresponding to the first amplitude of the comparison signals LPICl etc., see Fig. 12. The output signal LPIC is fed to an output circuit 38 which receives the video signal VIDEO and the hold signal PWAIT from the control circuit 2. The output circuit 38 generates an identification signal "PIC OUT" when the video signal VIDEO remains on amplitude Lo while hold signal PWAIT
is applied. The amplitude Lo identifies a signal-free sub-surface. This ensures that the decoded line pattern is followed by a signal-free trailing zone which corresponds to the trailing zone 58 of the PIC pattern.
The output circuit 38 is reset by the external reset signal "RESET IN" and thereupon applies a reset signal RESETA to the interim memory 34 and resets the latter for a new cycle. The interim memory is further reset by the over-flow reset signal "OV RESET" when one of the counters 6 to 12 signals an overflow.
Fig. 10 is a schematic representation of the organ-ization of the comparison table, for example the partial comparison table of PROM1 for comparing the quotient TC1/TC2.
The table comprises a memory matrix and its lines and columns have the appropriate binary addresses. In accordance with a preferred em~odiment of the decoder of the invention, a 5-bit representation has been selected. All memory positions with a specific value of the quotient of line address to column address lie on one line, the so-called expectancy line around which the expectancy field is located. Within the field all those memory positions are located which address quotients that fall in the predetermined value range. The counts TCl to TC4 are also emitted as 5-bit words. The ount TCl ` llSlZ~9 addresses the lines of the table, the count TC2 addresses the col~mns of the table.
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Claims (23)
1. In a method for identifying objects appearing at random positions in random orientation, and at random times on an image window and having, on a surface facing the image window, an identification in the form of a field which includes on at least one data track contrasting indicia with at least one contrasting line pattern identifying the posi-tion and the orientation of the data track and having a plurality of parallel lines with variable spacing and/or line widths, the image window being scanned line-by-line and a binary video signal being generated which corresponds to the scanned contrast sequence, the image window being, in a first method step, scanned under varying angles until a contrasting line pattern is detected, the position and alignment of the data field relative to the image window being determined in a second method step and, in a third method step, a raster scan in the direction of the data track being performed and the indicia present on the data track being read and decoded, the improvement to the method comprising the steps of identifying the contrasting line pattern by measuring the length of the overlapping light-dark intervals of the video signal, com-paring the successively measured interval lengths, generating a comparison signal having a first amplitude when two inter-val lengths which are being compared have a predetermined ratio to each other which corresponds to a corresponding spacing in the contrasting line pattern, and emitting an identification signal when, during each of a number of suc-cessive comparing steps as determined by the contrasting line pattern, a reference signal having a first amplitude is generated, and wherein the comparing of successively measured interval lengths is carried out in pairs in a two-dimensional comparison table within which the pos-sible discrete values of an interval length are assigned to table lines, and the possible discrete values of the next following measured interval length are assigned to table columns, and wherein an expected field is specified encompassing the positions on the table in which the quotient of the two successively measured compared in-terval lengths falls within a given value range, and including the step of generating the comparison or reference signal having said first amplitude when the compared interval lengths correspond to a table position within the expected field.
2. A method according to claim 1, wherein the expected field lies in an area of the table limited by a line and a column corresponding to minimum and maximum interval lengths.
3. A method according to claim 1, wherein first and second successively measured intervals which are to be compared are fed into an individual comparison table having its own expected field and being assigned to the first and second measured intervals.
4. A method according to claim 3, wherein dif-fering expected fields for corresponding successively mea-sured interval lengths of various contrasting line patterns are included in the individual comparison table.
5. A method according to claim 1, including the step of placing successively measured intervals into the comparison table in pairs after the later measured interval length has been measured.
6. A method according to claim 1, wherein the measuring step comprises the step of measuring the intervals of the video signal from one rising slope to the next rising slope and, overlapping therewith, from a falling slope lying between the rising slopes to the next falling slope.
7. A method according to claim 1 wherein the contrasting line pattern includes a lead zone of predeter-mined length which is free of signals, and including the step of initiating the measuring step only after a signal-free lead zone of the predetermined length has been detected in the video signal.
8. A method according to claim 1 including the step of terminating the measuring step when a measured inter-val length exceeds a predetermined maximum value which cor-responds to the maximum interval length present in the con-trasting line pattern.
9. A method according to claim 1 including the step of terminating the measuring step and initiating a new measuring step when the ratio of two successively measured interval lengths is outside the predetermined value range, resulting in the generation of a reference signal having a second amplitude.
10. A method according to claim 1 including the step of terminating the measuring step and initiating a new measuring step when a signal-free intermediate zone of pre-determined duration is detected in the video signal which corresponds in duration to the maximum scanning distance between lines of the contrasting line pattern.
11. A method according to claim 1 wherein the contrasting line pattern includes a signal-free trailing zone having a predetermined length, and including the step of emitting an identification signal only in response to detec-ting from the video signal a signal-free trailing zone of the predetermined length.
12. A method according to claim 1 wherein the measuring step includes the steps of counting the interval lengths digitally as a multiple of the given sync period to form a binary signal, and subsequently using the binary signal.
13. A method according to claim 1 including the step of scanning a given line of the image field n times, and emitting the identification signal only in response to iden-tifying a contrasting line pattern n times in succession.
14. In an apparatus for identifying objects appearing at random positions in random orientation, and at random times on an image window and having, on a surface facing the image window, an identification in the form of an image field which includes on at least one data track con-trasting indicia with at least one contrasting line pattern identifying the position and the orientation of the data track and having a plurality of parallel lines with variable spacing and/or line widths, the image window being scanned line-by-line and a binary video signal being generated which corresponds to the scanned contrast sequence, the image window being, in a first step, scanned under varying angles until a contrasting line pattern is detected, the position and alignment of the data field relative to the image window being determined in a second step and, in a third step, a raster scan in the direction of the data track being per-formed and the signals contained on the data track being read and decoded, the apparatus having an optoelectronic scanning device including a rotatable scanning raster which emits at the output the binary video signal corresponding to the image field which is scanned line-by-line and includes binarily the contrast pattern of the scanned line, a decoder for identi-fying the contrasting line pattern which identifies the position and orientation of at least one data track of a data field, means for aligning the scanning raster parallel to the data track and for reading the scanned indicia of the data track, the improvement to the decoder comprising a counting circuit which receives the video signal and counts the length of successive overlapping intervals of the video signal, at least one reference table for receiving successively counted interval lengths in pairs via a gate circuit and for emitting a comparison signal having a first amplitude when the com-pared interval lengths have a given ratio which corresponds to the ratio of the corresponding interval of the contrasting line pattern, and an evaluation circuit for generating an identification signal during a succession of a given number of comparison signals each having the first amplitude.
15. Apparatus according to claim 14, wherein the counting circuit includes a timing circuit for generating gate pulses which correspond to overlapping intervals of the video signal the pulse lengths of which is determined by successive rising slopes and by successive falling slopes of the video signal, respective counters activated by the gate pulses, the counters being jointly connected at their inputs with a sync generator, the counters generating a digital output defining the measured interval length, and means for applying the digital output to a reference table.
16. Apparatus according to claim 15, wherein the counting circuit includes means for detecting an overflow and for resetting the decoder when a counter overflows.
17. Apparatus according to claim 14, wherein the reference table comprises a two-dimensional read-only memory, wherein possible discrete counting values of a first interval length are addressed to associated lines of the read-only memory, wherein possible dicrete counting values of the subsequently counted interval lengths are addressed to associated columns of the read-only memory, and wherein an expected field within the memory encompasses the memory positions where the quotient of line address to column address falls within a given value range, so that a com-parison signal with a first amplitude is emitted when a memory position within the expected field is addressed, and a comparison signal with a second amplitude is emitted when a memory position outside the expected field is addressed.
18. Apparatus according to claim 17, including a separate read-only memory with its own expected field for each two successive interval counting values.
19. Apparatus according to claim 18, including means for addressing in pairs to the associated read-only memory successively counted interval length when the later counted interval length is counted out and the timing circuit emits a release signal for activating the gate disposed in advance of the memory.
20. Apparatus according to claim 17, wherein each read-only memory includes selectively addressable different expected fields for differing contrasting line patterns, and wherein the comparison signals associated with the different fields are selectively fed via a switch to an evaluation circuit.
21. Apparatus according to claim 14, wherein the evaluation circuit comprises an interim memory for storing the comparison signals until the last comparison signal is received and for feeding all comparison signals to separate inputs of an AND gate for emitting therewith an output signal when all comparison signals are present and have the first amplitude.
22. Apparatus according to claim 21, including an output circuit following the AND gate, the output circuit receiving as an input the video signal and a hold signal from the timing circuit and generating the identification signal whe, while the hold signal is applied, the video signal has a signal-free trailing section.
23. Apparatus according to claim 14, including a reset circuit receiving as its input the video signal and, at the start of each scan line, an external reset signal, the reset circuit emitting a reset signal when the video signal includes a signal-free section which is larger than the maximum scanning distance between the lines of the con-trasting line pattern, and when an external reset signal is applied, and including means for feeding the reset signal to the counters and to the timing circuit for resetting them.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DEP2915732.2 | 1979-04-19 | ||
| DE2915732A DE2915732C2 (en) | 1979-04-19 | 1979-04-19 | Method for identifying objects and apparatus for carrying out this method |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1151299A true CA1151299A (en) | 1983-08-02 |
Family
ID=6068660
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000349940A Expired CA1151299A (en) | 1979-04-19 | 1980-04-15 | Method and apparatus for identifying objects |
Country Status (11)
| Country | Link |
|---|---|
| EP (1) | EP0017950B1 (en) |
| JP (1) | JPS5614373A (en) |
| AT (1) | ATE4562T1 (en) |
| AU (1) | AU5755680A (en) |
| CA (1) | CA1151299A (en) |
| DE (1) | DE2915732C2 (en) |
| DK (1) | DK163480A (en) |
| ES (1) | ES490712A0 (en) |
| FI (1) | FI67633C (en) |
| IE (1) | IE50309B1 (en) |
| NO (1) | NO801128L (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3039191C2 (en) * | 1980-10-17 | 1984-10-04 | Scantron GmbH & Co Elektronische Lesegeräte KG, 6000 Frankfurt | Method for identifying objects and device for carrying out the method |
| JPH07104902B2 (en) * | 1986-10-14 | 1995-11-13 | 株式会社テック | Bar code reader |
| JP3811680B2 (en) * | 2003-01-29 | 2006-08-23 | 富士通株式会社 | Wiring board manufacturing method |
Family Cites Families (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3784792A (en) * | 1972-03-29 | 1974-01-08 | Monarch Marking Systems Inc | Coded record and methods of and apparatus for encoding and decoding records |
| DE2338561A1 (en) * | 1972-08-30 | 1974-05-09 | Scanner | METHOD AND DEVICE FOR IDENTIFYING OBJECTS |
| US3887792A (en) * | 1973-12-04 | 1975-06-03 | Scope Inc | Method and device for reading and decoding a delta-distance code |
| US3979577A (en) * | 1973-12-05 | 1976-09-07 | Data General Corporation | Code recognition record medium and technique |
| US3854036A (en) * | 1974-02-27 | 1974-12-10 | Singer Co | Tag reader to digital processor interface circuit |
| US3925761A (en) * | 1974-08-02 | 1975-12-09 | Ibm | Binary reference matrix for a character recognition machine |
| JPS52143711A (en) * | 1976-05-25 | 1977-11-30 | Nippon Telegr & Teleph Corp <Ntt> | Mark read-in system by facsimile |
| US4125765A (en) * | 1977-06-27 | 1978-11-14 | International Business Machines Corporation | Label find method and circuit |
-
1979
- 1979-04-19 DE DE2915732A patent/DE2915732C2/en not_active Expired
-
1980
- 1980-04-14 AT AT80101991T patent/ATE4562T1/en not_active IP Right Cessation
- 1980-04-14 EP EP80101991A patent/EP0017950B1/en not_active Expired
- 1980-04-15 FI FI801195A patent/FI67633C/en not_active IP Right Cessation
- 1980-04-15 IE IE767/80A patent/IE50309B1/en unknown
- 1980-04-15 CA CA000349940A patent/CA1151299A/en not_active Expired
- 1980-04-17 JP JP5156680A patent/JPS5614373A/en active Granted
- 1980-04-17 DK DK163480A patent/DK163480A/en not_active IP Right Cessation
- 1980-04-17 AU AU57556/80A patent/AU5755680A/en not_active Abandoned
- 1980-04-18 ES ES490712A patent/ES490712A0/en active Granted
- 1980-04-18 NO NO801128A patent/NO801128L/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| IE800767L (en) | 1980-10-19 |
| ES8202169A1 (en) | 1982-01-01 |
| DK163480A (en) | 1980-10-20 |
| AU5755680A (en) | 1980-10-23 |
| DE2915732A1 (en) | 1980-10-30 |
| IE50309B1 (en) | 1986-04-02 |
| EP0017950B1 (en) | 1983-08-31 |
| EP0017950A1 (en) | 1980-10-29 |
| JPS6318783B2 (en) | 1988-04-20 |
| FI67633C (en) | 1985-04-10 |
| FI801195A (en) | 1980-10-20 |
| FI67633B (en) | 1984-12-31 |
| DE2915732C2 (en) | 1983-09-29 |
| JPS5614373A (en) | 1981-02-12 |
| ES490712A0 (en) | 1982-01-01 |
| NO801128L (en) | 1980-10-20 |
| ATE4562T1 (en) | 1983-09-15 |
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